The present invention relates to packaging machines for producing containers, for example, from a web of packaging material, with liquid food or like contents, accommodated in the containers.
Packaging machines are already known which are adapted to form a web of packaging material into a tube having a closed lower end, fill liquid contents into the tube with the liquid level held at a specified level, transport the filled tube a distance at a time which distance corresponds to the length of one container, seal and cut the tube transversely thereof to form a pillowlike container, and eventually form the container into a rectangular parallelepipedal completed container, the tube being sealed and cut under the liquid level.
The conventional packaging machine wherein the tube is sealed and cut under the liquid level is likely to produce faulty seals if the contents contain a fibrous material, or the like, since such a material will be present at the portion to be sealed as an extraneous matter. Further, when the contents have a relatively high temperature of about 65 to about 85xc2x0 C., the portion sealed under the liquid level will not be fully cooled to become faulty. In the case where the contents filling the container contain ingredients which are likely to settle, it is desirable to shake the container to eliminate the deposit when so required. However, if the tube is sealed under the liquid level, the container is filled up with the contents and encounters difficulty in eliminating the deposit by shaking.
An object of the present invention is to overcome the above problems and to provide a packaging machine which is adapted to produce containers without permitting extraneous matter to be present in the portion to be sealed while permitting the sealed portion to be fully cooled to eliminate faulty seals, the containers being further shakable to eliminate settling of ingredients.
The present invention provides a packaging machine comprising a filling device for filling a tube of packaging material having an open upper end and a closed lower end with contents in a predetermined amount at a time, and a device for forming containers by sealing and cutting the filled tube transversely thereof into a length corresponding to one container at a time, the amount of contents to be filled into the container and the capacity of the container being so determined that the capacity is greater than the amount of contents to be filled.
With the packaging machine of the present invention, the amount of contents to be filled into the container and the capacity of the container are so determined that the capacity is greater than the amount of contents to be filled, so that the container is sealed at a position above the level of the contents within the container. This eliminates the likelihood that the contents will be in contact with the portion to be sealed, rendering the sealed portion free from extraneous matter, while the sealed portion can be efficiently cooled without being influenced by the temperature of the contents. These features eliminate faulty seals. Since the container is sealed with air remaining therein, the sealed container has an air layer therein. Because of the presence of the air layer, the container can be shaken to obviate the settling of ingredients.
The tube can be reliably filled with the contents in a specified amount at a time when the filling device comprises a filling pipe having the tube fitted therearound, a metering cylinder connected to the filling pipe, and an upstream check valve and a downstream check valve disposed upstream and downstream from the metering cylinder respectively.
When the filling pipe is provided at a lower end thereof with a discharge opening positioned in the vicinity of the lower end of the tube, and if the discharge opening is adapted to be opened and closed by the downstream check valve, the discharge opening can be reliably opened and closed by the downstream check valve to meter the contents more accurately, and can also be prevented from dripping.
When the tube has the open upper end positioned within a chamber, and if the chamber is held at a positive internal pressure, the container can be sealed while being held at a positive internal pressure. If the internal pressure of the container is insufficient, the container, which is circular in cross section when to be shaped to a rectangular or square form in cross section (see FIG. 2) before sealing, will not always be so shaped properly, whereas since the interior of the container is held at a positive pressure when to be sealed, the container can be accurately shaped to the desired form.
Preferably, the chamber has a blower connected thereto and is provided with a pressure relief valve.
The filling device may comprise a metering cylinder having therein a piston, which is connected by a rod to an eccentric wheel mounted on an output shaft of a motor. The amount of contents to be filled into the container is then variable by altering the radius of gyration of the eccentric wheel.
The forming device has sealing jaws openable and closable and movable upward and downward with the tube positioned therebetween, and the capacity of the container is variable by altering the stroke of the sealing jaws.